U.S. Pat. No. 3,842,260 discloses a prior art device for detecting blockage of optical paths.
U.S. Pat. No. 4,387,367 discloses a technology involving a problem of influences from light entering through undesired angles (external turbulent light) to which the present invention is directed.
U.S. Pat. Nos. 4,585,940, 4,490,801 and 4,243,879 disclose electrical and mechanical arrangements to overcome the problem.
A basic arrangement of the prior art optical sensor used in an optically activated automatic door is shown in FIG. 18 in which light emitting diodes (LED) or other light emitting elements and photo transistors or other light receptor elements are opposed and spaced by a distance. At inner positions of the light emitting elements 1 and light receptor elements 2 are mounted convergent lenses 103 and 104 made from acrylic resin or similar material. Since the convergent lenses 103 and 104 have a filtering function to permit selective transmission of invisible light such as infrared rays, an invisible optical path 5 is formed between the convergent lens 103 associated with the light emitting element 1 and the convergent lens 104 associated with the light receptor element 2. More specifically, a flux of light emitted from a light emitting portion 1a of the light emitting element 1 is focused by the lens 103 at the lens 104 which focuses the flux of light again at a light receptor portion 2a of the light receptor element 2. When a human body or other obstacle moves in between the space, the light path 5 is blocked, and the light blockage is detected. The convergent lenses 103 and 104 have a light converging function to prevent dispersion of beams of light and contributes to an improved detecting efficiency.
Some prior art optical sensors use high output light emitting elements to omit the convergent lens associated with the light emitting elements.
There are many kinds of coordinate input devices of electromagnetic induction type, electrostatic capacitance type, transparent electrode type, optical detection type and other types to manually input desired signals in a computer. Among them, the industry recognizes the high reliability and operability of the optical detection type device which is mounted on a front face of a display device so that a user can indicate a position on a coordinate system without contacting the detecting device, by simply putting his finger, etc. on a desired position on a display surface of the display device to block an optical path.
A prior art coordinate system input device of this type is shown in FIGS. 16, 19 and 20. FIG. 19 is a perspective view of the coordinate system input device mounted on a front face of a display device, FIG. 20 is a fragmentary cross-sectional view taken along a line including a light receptor element of the coordinate system input device, and FIG. 16 is a back elevation of the coordinate system input device from which a back plate is removed to expose the interior arrangement thereof.
The coordinate system input device generally comprises a frame member 201, arrays of LED or other light emitting elements 1, arrays of photo transistors or other light receptor elements 2 and an operational system 6. The frame member 201 is a rectangular molded member having an opening 202 at the center thereof. The light emitting elements 1 and light receptor elements 2 are mounted at the back of the frame member 201, i.e. between the frame member 201 and outer peripheries of a display surface 203a of a display device 203 including a cathode ray tube, etc. The operational system 6 detects the position of a blocked one of optical paths 5 formed by opposed light emitting elements 1 and light receptor elements 2 via an operating area A in a front portion of the display surface 203a and inputs the detected position in a host computer (not shown). Spaced and parallel arrays 214 of light emitting elements and spaced and parallel arrays 215 of light receptor elements form a frame-shaped array 213 of optical elements.
The light emitting elements 1 and light receptor elements 2 are fixed on a base board 207 mounted in the frame member 201 so that the light emitting portion 1a and the light receptor portion 2a of each associated pair of elements 1 and 2 are properly opposed. At the front face of the light receptor portions 2a of the light receptor elements 2 is placed a light shield 208 having light holes 208a of a predetermined diameter so that each light receptor element 2 receives light from associated one of the light emitting elements 1 and nothing else. An infrared ray filter 9 is mounted throughout the entire length of the rectangular outer margin of the operating area A and in front of the light shields 208 and light emitting elements 1 so as to selectively transmit infrared rays. Therefore, invisible optical paths 5 passing the infrared ray filter 9 are formed in the operating area A near the display surface 203a.
The following explanation is directed to how a coordinate system is inputted by the coordinate input device having the aforegoing arrangement. As shown in FIG. 19, when a finger 211 touches a desired position on the display surface 203a, the optical path 5 passing the position of the finger is blocked, and a coordinate system position is specified. More specifically, when the light emitting elements 1 in the array 214 sequentially emit light and scan the optical paths, and the optical path 5 blocked by the finger is detected by the light receptor element 2 as specific positions in X and Y directions. The blocked optical path 5 is defined by the operational system 6, and the specific position on the coordinate system is entered in a host computer (not shown).
In the described prior art, however, the directivity of light entering in the operating area A from the light emitting elements 1 is bad. Beside this, the light holes 208a must have sufficient diameter so as not to impair a required detection efficiency. However, such holes cannot ensure a sufficient optical directivity, and light from a light emitting element 1 sometimes reaches the wrong light receptor elements and causes an erroneous operation of the device.
Some other prior art devices use a light shield holder 216 shown in FIG. 17 in lieu of the light shield 208 to place the light receptor elements 2 in the light shield holder 216 so that light reaches the light receptor elements through light holes 216a. In this case, however, undesired light entering through a course other than the optical path 5 is reflected by inner walls of the light shield holder 216 and reaches the light receptor portions 2a. Therefore, this cannot improve the optical directivity yet.
In this connection, the inventors proposed a coordinage system input device shown in FIGS. 14 and 15 in which an infrared ray filter 9 itself has focusing portions formed integrally therewith along one surface thereof opposed to the operating area A. The focusing portions are opposed to the light emitting elements 1 or light receptor elements 2 respectively. According to this proposal, beams of light emitted from a light emitting portion 1a are properly oriented by the focusing portion 9a located ahead, and the optical directivity is improved. Additionally, the focusing portion 9a placed in front of the receptor portion 2a converges the flux of incident light to improve the detection efficiency.